This is the first in a series of three research briefs summarizing findings from the newest and most rigorous research related to racial and socioeconomic diversity in public schools. The studies on which this brief is based were published recently in three special issues of the peer-reviewed journal, "Teachers College Record," edited by Professors Roslyn Arlin Mickelson of the University of North Carolina at Charlotte and Kathryn Borman of the University of South Florida. The weight of evidence from these studies demonstrates that racially isolated, high-poverty schools tend to negatively influence math and science course-taking patterns and achievement as measured by test scores. Meanwhile, under certain conditions, lower poverty schools and schools that do not enroll highly disproportionate shares of African American and/or Latino students tend to be positively associated with math and science achievement. This research augments an already extensive body of work in this area, which has reached similar conclusions. However, the work published this year in "Teachers College Record" is particularly rigorous. It draws from several strong data bases and employs cutting-edge statistical methods. This comprehensive collection of studies pays meticulous attention to separating the discrete contributions that schools, teachers, families and students themselves make to a variety of important educational outcomes, such as test scores and graduation rates. The authors urge courts, policymakers, education rights lawyers, educators and others to use this new work as a guide in decisions and advocacy related to diversity, schooling and equal opportunity. [For the second report in this series, see "How the Racial and Socioeconomic Composition of Schools and Classrooms Contributes to Literacy, Behavioral Climate, Instructional Organization and High School Graduation Rates. Research Brief No. 2. Updated" (ED571626). For the third report in this series, see "The Impact of Racially Diverse Schools in a Democratic Society. Research Brief No. 3. Updated" (ED571627).]